On a worldwide basis, polyolefins are consumed in the greatest quantity (approximately 14 billion pounds in the U.S.A.). Applications include packaging for food, milk and detergents, as well as for large volume industrial chemicals, and for the manufacture of toys, caps, wire and cable jacketing, silos, automotive parts and medical supplies. Since these plastics are not biodegradable, disposition presents a major threat to the environment for municipalities and industry.
Though negative in the abovementioned respect, certain waste plastics do have certain inherent strengths. Since they are not biodegradable, they have a life cycle much longer than conventional materials such as wood. In addition, plastics can be tailor-made to improve their chemical, environmental, bacterial, fungal or other biological resistance. Also, their mechanical, electrical or flame-resistant properties can be modified as required for particular applications and a variety of technologies can be used which cannot be used with naturally occurring materials.
Unfortunately, only limited applications for waste plastics have been developed. For example, U.S. Pat. No. 4,003,866 teaches construction material made from thermoplastic resins and fillers, but requires the use of coating or encapsulating the filler in polyethylene or polypropylene wax.
These processes, however, entail a large number of processing steps and the properties of the products are not sufficiently improved to enable the products to be used in many applications.
Also, in U.S. Pat. No. 4,161,465, waste PVC was reconstituted with red mud, but this patent does not address recycling waste polyolefins.